Accurately timed gestations in Rhesus monkeys are used. Streptozotocin, 40-48 mg/kg, is administered intravenously to the adult female prior to or in the first trimester of pregnancy. This drug induces a glucose intolerant state secondary to pancreatic beta cell destruction. During the third trimester, acute experiments are performed under general anesthesia and aseptic surgical techniques. Cannulae are placed into both the maternal and fetal circulations to permit sequential sampling of blood. A catheter is placed transuterine into the fetal stomach via the mouth and glucose solution is injected into the stomach lumen. Blood aliquots are analyzed for glucose, free fatty acids, insulin growth hormone, and glucagon using biochemical and radioimmunoassay procedures. After performing the same experiment on the newborn in the first day of life, tissue is examined histologically from both mother and conceptus. The primary focus of this work has been in progress for several years.